Electrical devices that interact with light are well known. Examples include light-emitting diodes (which emit light), solar cell modules (which harvest light and turn it into electricity), and display screens (which may alter the light that they reflect). Most devices of this type use glass in one form or another as the key, transparent substrate material. This is often problematic however, since glass is typically fragile, heavy, expensive, and generally not well-suited to high-volume, low-cost mass-production. For this reason there is increasing interest in using cheaper, transparent polymeric materials in place of glass in devices of this type. Ideally, this will be combined with simple and inexpensive fabrication techniques for the devices themselves, such as the use of commercial printing processes.
One problem in this respect is to integrate a transparent polymer substrate into the fabrication of flexible electrical devices. Several approaches have been trialled and are being used. A common one (exemplified by the flexible touch-screen disclosed in EP 0348229) is to employ a transparent polymer sheet which has been coated on one side with a transparent electrically conducting layer. The sheet acts as a transparent electrode upon which the remainder of the device is built, usually as a multi-layer structure.
Another approach (exemplified by the photovoltaic device described in DE 19846160), is to fabricate the device on a non-transparent, flexible polymer film and then overlay a transparent polymer film upon it, to thereby exclude vapour, oxygen, or dust from the device.
While techniques such as those described above are technically successful, they are typically not amenable to high volume, low-cost mass-production manufacturing, especially in respect of devices which interact with light. The cost of manufacturing such devices may, however, be a critical factor in their physical uptake by society. Indeed, in many cases it is purely the cost and complexity of manufacturing such devices that has halted their general use and application.
A range of electrical devices are currently manufactured in flexible, low-profile formats. This includes batteries, capacitors, and super-capacitors which employ flexible polymeric bases or packaging elements. For example, JP7037559, JP11086807, EP0499005, KR20010029825, JP3034519, and U.S. Pat. No. 5,650,243 describe batteries, capacitors, or super-capacitors which are manufactured by laminating such devices between two or more polymer films. Batteries, capacitors, and super-capacitors are generally far less demanding to manufacture than light-modulating devices since they do not require optical transparency in the flexible polymeric components and their layered arrangement is typically much more forgiving of minor variations in the layer thicknesses. Light-modulating devices are notoriously sensitive such variations, which often destroy their utility completely. The laminating polymers in the abovementioned batteries, capacitors, and super-capacitors are therefore primarily incorporated for the purposes of excluding vapour, oxygen, or dust, or for making such devices more rugged.
In a related area, hydrogen (H2) has long been considered an ideal fuel for the future. When burned in the presence of oxygen (O2), hydrogen produces water (H2O) as the only waste product. It therefore offers a clean, non-polluting alternative to fossil fuels.
Hydrogen has the added advantage that its reaction with oxygen may be made to take place in a solid-state device known as a fuel cell, which harnesses the resulting energy not as heat or pressure, but as an electrical current. Fuel cells offer greater inherent energetic efficiency than simple combustion of the type employed in, for example, internal combustion engines. A convenient source of hydrogen is the solar-powered splitting of water into hydrogen (H2) and oxygen (O2).
Hydrogen made from water using sunlight prospectively offers an abundant, renewable, clean energy source. However, no practical and economic device, or method of manufacture thereof, exists to facilitate this reaction. The potential of solar-produced hydrogen has, consequently, never been realized.
There is a need for improved water-splitting devices and/or methods for the improved manufacture thereof which address or at least ameliorate one or more problems inherent in the prior art.
The reference in this specification to any prior publication (or information derived from the prior publication), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from the prior publication) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.